Compound action cutting snips typically include a pair of handles connected to a pivot point and a pair of blades pivotally mounted on the handles and pivotally connected to each other at a separate pivot point. The compound action of the pivoting handles driving the pivoting blades of this type of snips provides for relatively greater force at the cutting blades than is produced by single pivot snips.
One type of compound action snips, aviation snips, are commonly used for cutting sheet metal. Aviation snips by convention have a cutting length of 1 to 1.5 inches in straight-line cutting snips, and a cutting length of about 1.75 inches for curved cutting snips. The maximum cutting length is believed to represent a limit imposed by the force required to close the ends of the blades through the material.
The relatively short cutting length of aviation snips makes them inconvenient for use for other materials where long cuts must be made, for example, cutting thin sheet material such a vinyl siding. Tinner snips, which are used for material such as vinyl siding, are single pivot tools that have relatively long handles and blades. These are heavy and can be difficult for a worker standing on a ladder to manipulate.
The present invention provides general purpose snips that can be used for a variety of materials. It has been found that a cutting snips can be provided with a more efficient cutting action without significant loss of cutting force at the blade tips by the arrangement of the cutting blades and handles described in more detail below.
The snips according to the present invention include a pair of handles mutually connected at a handle pivot, and a pair of cutting blades, each blade having a proximal end pivotally attached to a distal portion of one of the handles, and the blades being mutually connected at a blade pivot so that converging movement of the handles causes converging movement of the blades.
According to the invention, the blades have a maximum cutting length of at least 2.5 inches, and preferably in a range of 2.5 to 3.5 inches, and more preferably 2.75 inches. A ratio of the maximum cutting length to a length of the handles is at least 0.4. This relationship provides a tool that is easily handled and has an unexpected cutting efficiency throughout the range of cutting action.
According to another aspect of the invention, a ratio of the maximum cutting length of the blades to the length of the handles is at least 0.4 and preferably in a range of about 0.4 to 0.6.
According to yet another aspect of the invention, the handles are at a proximal portion of the snips, the blades correspondingly being at a distal portion of the snips, and the handle pivot is located proximal to and spaced from the blade pivot.
The blades may be both formed with honed cutting edges. Alternatively, a first of the blades may be formed with a serrated anvil surface substantially perpendicular to the first blade edge. The serrated anvil surface provides means for gripping a workpiece, and a second of the blades is formed with a honed cutting edge that moves against the edge of the anvil to cut the workpiece.
The snips according to the invention provides a cutting action that is more efficient than conventional compound action snips by virtue of the geometry of the blades and handles. The movement of the handles, which changes the relative orientation of the blades, causes a change in the effective cutting length, that is, the distance from the point at which the blade edges cross to the tips of the blade. The snips according to the invention are configured so that a ratio of the change in effective cutting length to angular movement of the handles is at least 0.05 inches/degree and more preferably in a range of 0.05 to 0.09 inches/degree. This more than 50% greater than the corresponding ratio in conventional snips and provides an advantage in using the snips.
According to the present invention, the geometry of the snips provides a ratio of a linear distance between tips of the blades in the open position and a linear distance between free ends of the handles in the open position that is at least 0.35.